Forecasting the cross correlation of Terahertz Intensity Mapper [CII] line intensity maps with Euclid galaxies

We forecast that the Terahertz Intensity Mapper (TIM) cross-correlated with Euclid’s Fornax deep field (EDF-F), TIM$\times$EDF-F, will detect the [CII]-galaxy cross-power spectrum at a median redshift of 1.1 with $\gtrsim 7\sigma$ confidence. The Poisson component of the cross-power spectrum at $0.1\le k\le 10$ hMpc${}^{-1}$ (i.e. cross-shot noise) will be detected at $\gtrsim 3\sigma$ in 4 bins spanning $0.5<z<1.7$. This measurement will constrain the mean [CII] specific intensity over half of cosmic history and assess the degree to which Euclid-selected galaxies account for the [CII] intensity observed by TIM. We find that TIM can detect the cross-power spectrum across a wide range of [CII] intensity models.